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    Siliceous Micro-Fossils: Diatoms

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    Anagha mohan
    Diatoms are a type of algae that have silica cell walls called frustules. There are over 16,000 species of diatoms grouped into two main orders - centric diatoms which are radially symmetric, and pennate diatoms which are bilaterally symmetric. Diatoms are found in almost all aquatic environments and have intricate structures like areolae, striae, and raphe that distinguish different species. They first appeared in the fossil record in the Jurassic period and are useful for paleoenvironmental reconstruction.

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    Siliceous Micro-Fossils: Diatoms

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    Anagha mohan
    39 views11 pages
    Diatoms are a type of algae that have silica cell walls called frustules. There are over 16,000 species of diatoms grouped into two main orders - centric diatoms which are radially symmetric, and pennate diatoms which are bilaterally symmetric. Diatoms are found in almost all aquatic environments and have intricate structures like areolae, striae, and raphe that distinguish different species. They first appeared in the fossil record in the Jurassic period and are useful for paleoenvironmental reconstruction.

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    DIATOMS

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    Diatoms are a type of algae that have silica cell walls called frustules. There are over 16,000 species of diatoms grouped into two main orders - centric diatoms which are radially symmetric, and pennate diatoms which are bilaterally symmetric. Diatoms are found in almost all aquatic environments and have intricate structures like areolae, striae, and raphe that distinguish different species. They first appeared in the fossil record in the Jurassic period and are useful for paleoenvironmental reconstruction.

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    © All Rights Reserved
    Download as PPSX, PDF, TXT or read online from Scribd
    Download as ppsx, pdf, or txt
    39 views11 pages

    Siliceous Micro-Fossils: Diatoms

    Uploaded by

    Anagha mohan
    Diatoms are a type of algae that have silica cell walls called frustules. There are over 16,000 species of diatoms grouped into two main orders - centric diatoms which are radially symmetric, and pennate diatoms which are bilaterally symmetric. Diatoms are found in almost all aquatic environments and have intricate structures like areolae, striae, and raphe that distinguish different species. They first appeared in the fossil record in the Jurassic period and are useful for paleoenvironmental reconstruction.

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    Download as ppsx, pdf, or txt
    of 11

    SILICEOUS

    MICRO-FOSSILS
    DIATOMS
    SILICEOUS MICRO
    FOSSILS

     Protists with shells


    constructed of OPALINE
    (amorphous SiO2). 3 MAJOR GROUPS OF SILICEOUS MICRO
    FOSSILS :
     Prevail in sediments
    deposited in high latitudes.  Radiolarians
     Diatoms
     Silicoflagellates
    DIATOMS

     Photosynthesizing algae that have a siliceous skeleton called FRUSTULE.


     Often referred to as ‘Jewels of the sea’ or ‘living opals’ due to their optical properties.
     Found in almost every aquatic environment including fresh and marine waters.
     There are about 16,000 species grouped under 200 genera.
     They commonly occur as Epiphytes( an organism that grows on the surface of a plant).
    SCIENTIFIC CLASSIFICATION

     CLADE - SAR

     PHYLUM- Ochrophyta

     SUBPHYLUM- Khakista

     CLASS- Bacillariophyceae
    CLASSIFICATION

     CLASS BACILLARIOPHYCEAE is divided into mainly 2 orders :


    1. Order Centrales.
    2. Order Pennales.
    DIFFERENCE B/W CENTRIC AND
    PENNATE DIATOMS
    CENTRIC DIATOMS PENNATE DIATOMS
     Shape and size varies  Mainly boat shaped.
     Radially symmetric.  Bilaterally symmetric.
     Discoid chloroplast.  Elongated chloroplast.
     Raphe is absent.  Raphe is present.
     Radially arranged striations.  Pinnate striations.
    STRUCTURE OF DIATOMS

     Generally 2-200 micrometers in size.


     Consists of hard and porous cell walls called frustules composed primarily of silica.
     The cell consists of 2 halves, each containing an essentially flat plate, or valve or a girdle
    band.
     One half is called HYPOTHECA which is slightly smaller than the other half, EPITHECA.
     Cell of diatoms consists of nucleus, nucleolus, golgi apparatus, mitochondria etc..
    INTRICATE STRUCTURE
    OF DIATOMS

    1. AREOLAE : hexagonal/polygonal
    box like perforation with a sieve
    present on the surface of diatom.
    2. STRIAE: pores/ punctures in a line
    on the surface.
    3. RAPHE- slit in the valves.
    4. STIGMATA- holes through valve
    surface which looks rounded
    externally but with an internal slit.
    5. PUNCTAE- spots or small
    perforations on the surface.
    6. POLAR NODULES- thickening of
    wall at the distal ends of the raphe.
    STRATIGRAPHIC RANGE

     First recorded occurrence in JURASSIC.

     Earliest recorder well preserved diatoms are mainly centric forms.

     They occurred in Aptian-Albian stages of the Cretaceous.

     The oldest fossil: Specimen of genus Hemiaulus in Late Jurassic aged amber from
    Thailand.
    APPLICATIONS

     DIATOMACEOUS EARTH is a type of powder made from sediment of fossilized algae


    found in bodies of water.
     Extensively used in Paleo-environmental studies particularly in Paleo-oceanography.
     Employed in Toxicity Testing and Eutrophication of aqueous ecosystems.
     Diatoms are an important source of food for aquatic animals.
     Diatoms are chemically inert and are used in filtration of sugar.
    THANK YOU!!

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